Jet engine noise suppression nozzle with multiple settings



Oct. 30, 1962 J. A. LAWLER ETAL 3,061,038

JET ENGINE NOISE SUPPRESSION NOZZLE WITH MULTIPLE SETTINGS Filed on. 30.1959 5 Sheets-Sheet 1 INVENIORS' fa/0v 4. 1/1/4 45? W11. 404M ,4.FEM/Amer 6M 454m .Oct. 30, 1962 J. A. LAWLER ETAL 3,061,038

JET ENGINE NOISE SUPPRESSION NOZZLE WITH MULTIPLE SETTINGS Filed Oct.30. 1959 207: 5 Sheets-Sheet 2 l/ 6 206 o 290. V 40 4? 5e ,4 r roe/vim?Oct. 30, 1962 J. A. LAWLER ETAL JET ENGINE NOISE SUPPRESSION NOZZLE WITHMULTIPLE SETTINGS 5 Sheets-Sheet 3 Filed Oct. 30. 1959 INVENTOR Jay/v A.44 wa w/u/nM/t PEI/714A?- Oct. 30, 1962 J. A. LAWLER ETAL 3,061,038

JET ENGINE NOISE SUPPRESSION NOZZLE WITH MULTIPLE SETTINGS Filed Oct.30. 1959 5 Sheets-Sheet 4 IN VEN TORS'. f0/M A. LA wu-z Y W14 z MMA.FEM/HA E7 B Oct. 30, 1962 LAwLER ETAL 3,061,038

JET ENGINE NOISE SUPPRESSION NOZZLE WITH MULTIPLE SETTINGS Filed Oct.30, 1959 5 Sheets-Sheet 5 JNVENTORjg} r/Ol/A/ 4. MW Y Wu; MM/l. ,emwmerB M, {M

United tes Patent $961,933 JET ENGINE NOISE SUPPRESSION NOZZLE WITHMULTIPLE SETTINGS John A. Lawler, Seattle, and William A. Reinhart,Bellevue, Wash, assignors to Boeing Airplane Company, Seattle, Wash, acorporation of Delaware Filed Oct. 30, 1959, Ser. No. 849,826 Claims.(Cl. 18133) This invention relates to improvements in low-noise nozzlesfor jet propulsion engines and is directed primarily to the provision ofefficient and practicable nozzles which, in their cruise setting,achieve moderate but sufi'icient noise suppression for operatingrequirements, whereas in the take-ofi setting produce maximum noisesuppression. The invention is herein illustratively described byreference to the presently preferred embodiments thereof; however, itwill be recognized that certain modifications and changes therein withrespect to details may be made without departing from the underlyingessentials involved.

Experience has shown that a moderate amount of jet noise suppression isdesirable during normal flight conditions in order to avoid structuralvibration problems and passenger discomfort in jet aircraft. However,when a jet airplane is climbing in the vicinity of an airport, such asfrom an altitude of 400 to 1200 feet, much greater noise suppression isdesirable in order to avoid disturbance of nearby residentialcommunities. No satisfactory fixed-type suppression nozzle has yet beendiscovered which achieves suppression for takeoff and climb operationwhich does not also introduce excessive performance losses, bothinternal and external, for efficient operation during normal flight orcruise conditions. Nevertheless, fairly large losses can be toleratedduring climb if necessary in order to gain the requisite noisereduction.

With these considerations in mind, together with others hereinaftermentioned or known in the art, the present invention proceeds to theprovision of a multiple setting noise suppression nozzle which satisfiesthe different operating requirements mentioned above in a practicableand efiicient manner.

More specifically the invention provides a compact and efiicient nozzleof this type which in the stowed position of the extendable elementsimposes minimum drag accompanied by efiicient jet operation withmoderate noise suppression. In the extended position of the nozzleelements, for achieving maximum noise suppression, net effective orificearea in the exit plane, matching engine load requirements, is maintainedapproximately the same as in the cruise setting.

In the disclosed, preferred embodiments the peripheral nozzle troughs orchannels, which guide slipstream air into the regions between jet streambranches or lobes formed by these troughs, produce moderate noisesuppression for cruise operation. In both illustrated emmodiments thisbasic nozzle configuration is modified for attaining maximum noisesuppression by raising or extending a plurality of auxiliary nozzleducts, normally stowed in the channels. When extended, these auxiliaryducts scoop gas from the nozzle and discharge it rearwardly andoutwardly at spaced locations about the nozzle periphery, hence in adispersed manner promoting rapid admixture with slipstream air. Partialreduction of the normal exit opening is effected in one case by multiplyapertured doors which close with auxiliary nozzle extension, and therebypermit restricted discharge of gases supplementally to that from theauxiliary ducts. In another case the cruise lobes are enhanced ordeepened by extension of tabs or doors into the jet core region inconjunction with auxiliary duet extension.

An important feature of the invention resides in the nesting of theextendable nozzle ducts in the channels or troughs which define thecruise orifice lobes. A further feature pertains to the pivotal mountingof these auxiliary ducts between the trough sides so that when swungoutwardly to radially extended position their inner ends communicatewith the nozzle interior to intercept or receive gases for discharge.

An additional feature resides in the arrangement by which the retractedauxiliary ducts themselves serve as guiding or fairing surfaces alongwhich slipstream air flows efiiciently into the regions between jetstream lobes, thus producing noise suppression with minimum loss fromdrag in the cruise condition.

The foregoing and other features, objects and advantages of theinvention will become more fully evident from the following descriptionbased on the accompanying drawings.

FIGURE 1 is a rear perspective view of the preferred form of theimproved multiple setting nozzle in cruise position.

IGURE 2 is a similar view with the nozzle in maximum noise suppressionor take-off position.

FIGURE 3 is a rear View of the nozzle in the position shown in FIGURE 2,with parts broken away for corn venience in illustration.

FIGURE 4 is a rear view of the nozzle in the position shown in FIGURE 1.

FIGURE 5 is a side view of the improved nozzle in cruise position withparts broken away approximately along a longitudinal midplane in orderto show details of construction.

FIGURE 6 is a view similar to FIGURE 5 with the nozzle in the take-offsetting and with still other parts broken away for convenience ofillustration.

FIGURE 7 is a sectional side view with parts broken away showing amodified nozzle configuration, with the nozzle parts in the cruisesetting.

FIGURE 8 is a rear view with parts broken away showing the samemodification with the parts positioned as in FIGURE 7.

FIGURE 9 is a View similar to FIGURE 7 of the modified nozzle with partsbroken away to show certain details, with the nozzle parts in thetake-off or maximum noise suppression setting.

FIGURE 10 is a rear View with parts broken away showing the nozzlepositioned as in FIGURE 9.

Referring to the drawings, in the embodiment shown in FIGURES l to 6,inclusive, the nozzle discharge opening 10, generally of annular form isdefined between the outer wall or tail pipe 12 and the central tail coneor plug 15 which tapers rearwardly to a tip and is so shaped in relationto the outer wall as to define a convergentdivergent orifice. Tail pipe12 has a rearward extension 12a, which commences at a location in thevicinity of the rear terminus of plug 15 and which is of essentiallyconstant or uniform cross section. This extension 12a is characterizedby longitudinal troughs 14, located at regular intervals about itsperiphery. These troughs open upstream into the nozzle interior It). Inthe example, four such troughs at degree spacings are formed in thenozzle extension 12a, but it will be recognized that the number andspacing thereof is subject to variation.

An external cowl or nacelle wall 16 surrounds the nozzle wall 12, withspacing 18 therebetween for housing mechanical and electrical controlsand actuators including those to be described. Suitable structuralreinforcing flanges provide means for interconnecting the cowl andnozzle walls and imparting the necessary rigidity and strength thereto,but are of secondary concern for present purposes, hence require nodetailed description herein.

Auxiliary nozzle ducts 2d normally lie nested in the respective troughs14. The then inner wall a of each duct lies in close proximity to or incontact with the trough base whereas its outer wall 2%, convergingrearwardly with the inner wall 20a, lies at an incline to the nozzleaxis A and in general extends the rearwardly tapered contour of theouter cowl 16. The forward edge of outer wall 20b is pivoted at 22 on atransverse axis which lies generally in a plane perpendicular to theengine axis A, which plane is substantially coincident with the planedefined by the forward edges of the troughs 14. This pivotal support forthe auxiliary ducts 2!? permits them to be swung from their nestedposition, shown in FIG- URE 5, outwardly to their extended positionshown in FIGURE 6 in which their former inner walls 20a are nowapproximately perpendicular to the engine axis A. The walls 20a aremultiply apertured and preferably include louvers or vanes 20c which areslanted outwardly and to the rear in order to direct the gases whichflow through the extended auxiliary ducts 2% in a rearward and outwarddirection for noise suppression operation. As will be noted, the ducts20' are formed with open sides 20d which, with the ducts extended, facedirectly upstream and largely occupy the cross-section of the troughs 14fronting upstream into the nozzle interior 10. A curved wall portion 20cextends rearwardly and outwardly from the inner edge of opening 20d inan are centered on axis 22 to the wall Ztla. This curved wall 20cprovides an etiicient directing or turning surface for air scooped intothe duct opening 20d with the duct extended, directing such airoutwardly and through the opening defined through the slanted vane Ztlc.In the retracted or nested position of the ducts 20, the curved surfaceswe extend forwardly and outwardly from the forward edges of the troughs14 to the nozzle outer wall 12 and thus provide fairing surfaces whichefliciently turn the gases inwardly past the trough ends and toward thetail cone 15.

Thus, the troughs I4 serve as stream divider elements in the nozzleorifice splitting the jet into lobes or branches and at the same timechanneling slipstream air into the spaces between lobes for rapidmixture therewith in the cruise setting of the nozzle.

In the extended or raised position of the auxiliary ducts 20, gasesscooped into these ducts through the openings 20d are discharged inrearwardly and outwardly fanning streams which in themselves are brokenup for a rapid admixture with slipstream air, thereby adding to theeffect of the main nozzle corrugations 14 in reducing engine jet noise.

Nozzle area compensation in this embodiment is achieved by providingmultiply apertured doors 30, which are swung into blocking positionacross the discharge ends of the nozzle orifice lobes 14 (FIGURE 2) whenthe auxiliary ducts 20 are extended. These doors are formed in two partsrespectively hinged at a and Stlb to the generally aligned rear edges ofthe troughs 14 and struts 32. The inner ends of the struts terminate onan island member 34 of streamline configuration centered on engine axisA. Preferably tabs 36, hinged with the door sections, partially closethe elements of orifice area lying generally between the base circle ofthe troughs and the island member 34 when the doors close. The residualopen area provided around these tabs, the composite area afiorded by theapertures in doors 3t), and the effective open area through theauxiliary ducts, total approximately the same as the open area throughthe orifice in the cruise setting.

While any suitable actuating means for controlling the position of theauxiliary ducts 2t) and of the doors 30 may be employed consistent withthe design requirements of jet engine nozzles, that illustrated performsthe necessary functions in a direct and simple manner. Thus, within thespace 18 pneumatic or hydraulic actuators having piston rods 42 areconnected to actuator links 44 which extend generally rearwardly topivotal connections 46 with the outer sides 20b of the respective ducts20.

These actuators and actuating connections provide for extension andretraction movements of the doors and the auxiliary ducts. Crank arms50, rigidly connected to the ducts 20 to pivot therewith about pivots22, are connected by actuator links 52 to the outer ends of the doors at54-, through universal couplings, in order to swing the doors conjointlywith movement of the ducts, so that the doors close when the ducts 2dare extended, and open when the ducts are retracted as depicted. Thereare two such crank arms '50 associated with each auxiliary duct 20, oneon either side thereof, and an actuating link 52 connected between theswinging end of each such crank arm and one door of each of the adjacentsets (FIGURE 3).

In order to limit the radially projecting length of the ducts 2t) tothat which is useful for auxiliary nozzle pur poses, and so that dragwill be minimized, the rearwardly tapered (when nested) form of theseducts does not extend to a point or tip, but terminates in a blunt end20f. This assures that the outermost aperture in the wall 20a with theduct extended may be located near the end without the volumetric flowthrough it being restricted unduly by undue narrowing of the duct atthat point. Preferably the aft end of each duct 20 in nested positionlies forwardly of the aft end of the associated trough 14 and theresulting discontinuity which otherwise occurs is filled or occupied bya fairing plug 14b secured to the base wall of the associated trough 14and extending transversely between opposite sides thereof as shown.

In the modification shown in FIGURES 7 through 10 the generally annularnozzle discharge space defined between the plug or tail cone 62 andouter wall 64, is modified by the presence of the troughs 66. Acorrugated or lobed orifice efiect results comprising the lobe spaces 68formed between the troughs, and which are joined with the generally opencentral region within the nozzle. The troughs 66 increase rearwardly indepth, whereas the peripheral duct wall between troughs remains ofsubstantially constant diameter over the length of the troughs. Thetroughed formations extend substantially from a point, lengthwise of thenozzle, approximately opposite the maximum diameter point of the tailcone, to the after end or exit plane of the nozzle. Such a nozzleconfiguration has moderate noise suppression characteristics and low.drag. Slipstream air flows rearwardly and inwardly through the troughsto discharge into the spaces between the jet lobes issuing from regions68. The ducts 70 viewed in nested position (FIGURE 7) are of rearwardlytapered form so as to place their inner walls 78 in proximity to or incontact with the inclined base walls of the troughs 66 while their outerwalls 72 lie substantially coplanar with the outer edges of the troughs.Although the troughs are occupied by the auxiliary ducts 70 in thecruise position, the presence of these ducts in the troughs does notappreciably interfere with such flow of slipstream air into and alongthe troughs because the outer walls 72 of the ducts 70 have a pluraliytof apertures 74 therein defined between the slanted louvers or vanes76, which are inclined rearwardly and inwardly (FIGURE 7). Slipstreamair enters through these apertures and through the end opening 79 todischarge rearwardly as described. A flap valve 80, normally open, isforced closed by gas pressure to seal the end opening 79 when the duct70 is extended as in FIGURE 9.

The rearward end of the troughs 70 in their nested position lieforwardly of the aft end of the nozzle and are pivoted at 82 ontransverse axes at their inner rearward edges so as to permit swingingthereof between the nested position of FIGURE 7 and the extendedposition of FIGURE 9 wherein they lie substantially at right angles tothe engine axis A. Just aft of the pivot point 82, the base of eachtrough 66 is provided with a relatively large opening 84 through whichgases may flow radially outward into the interior of the duct 70 in itsextended position (FIG- URE 9). Normally, this opening 84 is closed by aflap 86 which pivots at 88 on a transverse axis located at the afteredge of the trough base. This cover flap 86 is swung into a positiontransverse to the axis A, however, when the duct 70 is extended so as toblock flow of gases rearwardly from the nozzle in the region directlybehind aperture 84. Resultant blockage of flow gives rise to therequisite outflow of gases into the extended ducts 70 and at the sametime reduces the normal orifice area approximately by the amount thatsuch area is effectively increased by the extension of the ducts anduncovering of side openings 84. Consequently, the efiective nozzle arearemains approximately the same in the cruise position as in the maximumthrust position and is thereby continuously matched to enginerequirements.

For actuation purposes, a pneumatic or hydraulic actuator 90 is housedwithin the hollow interior of the tail cone 62 and has a piston rod 92which extends axially through the after end thereof. This rod carries onits outer end a fitting 94 which comprises the conical terminus of thetail cone when the actuator is retracted (FIGURE 7). This fitting 94serves as a means by which to connect the after end of the piston rod 92to the flaps 86 through actuating links 96, thereby to swing the flapsdownwardly into the position of FIGURE 9 by extension of the piston rod92, and to swing the flaps upwardly into the position closing theopenings 84 (FIGURE 7) by retraction of the piston rod. Additionalactuating links 98 interconnecting the flaps 86 with the auxiliary ducts70, through openings 84, serve to actuate the ducts be tween theirextended and retracted positions conjointly with movement of the flaps.

These and other aspects of the invention, including details of designand operation of the preferred embodiments shown, will be evident tothose skilled in the art, after becoming familiar with the presentdisclosure of such embodiments.

We claim as our invention:

1. Jet propulsion engine noise suppression nozzle means comprising anozzle discharge duct opening rearwardly for discharge of gasestherethrough, said nozzle duct having a plurality of elongated flowdivider elements extending longitudinally thereof at spaced locationsabout the duct periphery and, at the ducts discharge end, projectinggenerally radially inward to produce a corrugated nozzle effect dividingat least the jet periphery into a plurality of spaced lobes betweenwhich slipstream air is drawn with attendant moderate jet noisereduction, said flow divider elements comprising channels laterally opento the slipstream, and means to increase noise reduction comprising aplurality of elongated auxiliary ducts normally nested in the respectivechannels extending lengthwise therein with their then outer sidesinclined rearwardly and inwardly of the nozzle, said auxiliary ductsbeing pivotally mounted by their forward ends therein to swing outwardlyinto extended position disposed generally transversely to the directionof discharge, said extended auxiliary ducts having apertured dischargesides which face aft and having reception openings at their pivotedinner ends which communicate with the nozzle interior to admit gases fordischarge through said apertured sides, compensating means operable torestrict nozzle opening approximately equally to the increase thereofelfectively produced by auxiliary duct extension, and means operable toextend the auxiliary ducts and operate the compensating means inconjunction therewith, thereby to increase noise reduction and maintaineffective nozzle opening approximately constant.

2. Jet propulsion engine noise suppression nozzle means comprising anozzle discharge duct opening rearwardly for discharge of gasestherethrough, said nozzle duct having a plurality of elongatedtrough-like elements extending longitudinally thereof at spacedlocations about the duct periphery and exposed laterally to theslipstream to produce a corrugated nozzle effect at the discharge end ofsaid duct, and means to increase noise reduction comprising a pluralityof elongated auxiliary ducts normally nested in the bases of therespective troughs and pivotally mounted therein to swing outwardly intoextended position disposed generally transversely to the direction ofdischarge, said extended auxiliary ducts having apertured dischargesides which face aft and having entrance openings at their pivoted innerends communicating with the nozzle interior to admit gases from thenozzle interior for discharge through said apertured sides, compensatingmeans operable to restrict the composite nozzle opening approximatelyequally to the increase thereof effectively produced by auxiliary ductextension, and means operable to extend the auxilary ducts and operatethe compensating means in conjunction therewith, thereby to increasenoise reduction and maintain effective nozzle opening approximatelyconstant, the troughs at the discharge end of the nozzle being deeperthan the auxiliary ducts nested therein, whereby the corrugated nozzleeffect is maintained with the auxiliary ducts in nested position.

3. The nozzle means defined in claim 2, wherein the compensating meanscomprise door-like flaps hinged on the ends of the trough-like elementsto swing between retracted position substantially parallel to the nozzledischarge and operative position partially blocking the discharge of gasthrough the nozzle.

4. The nozzle means defined in claim 3, wherein the door-like flaps arehinged in pairs on respectively opposite sides of the trough-likeelements and have a plurality of spaced discharge apertures thereinpermitting limited discharge of gases therethrough when in closedposition.

5. The nozzle means defined in claim 3, wherein the trough-like elementshave less depth than the distance to the nozzle center at the exit planeto produce a jet form having a central core region with surroundinglobes, and the door-like flaps are hinged on the base edges of thetrough-like elements to project into and divide said core region therebyto increase the depth of said lobes.

6. The nozzle means defined in claim 2, wherein the apertured dischargesides of the extended auxiliary ducts include flow-directing louversslanted outwardly and rearwardly therein.

7. Jet propulsion engine noise suppression nozzlemeans comprising anozzle discharge duct opening rearwardly for discharge of gasestherethrough, said nozzle duct having a plurality of elongatedtrough-like ele ments extending longitudinally thereof at spacedlocations about the duct periphery and exposed laterally to theslipstream to produce a corrugated nozzle effect at the discharge end ofsaid duct, and means to increase noise reduction comprising a pluralityof elongated auxiliary ducts normally nested in the bases of therespective troughs with their outer walls set inwardly from the nozzleperiphery therein to maintain the corrugated nozzle effect at thedischarge end of the nozzle, said auxiliary ducts being pivotallymounted in the respective troughs to swing outwardly into extendedposition disposed generally transversely to the direction of discharge,said extended auxiliary ducts having apertured discharge sides whichface aft and having means to scoop gases from the nozzle interior fordischarge through said apertured sides, and compensating means operableto restrict nozzle opening approximately equally to the increase thereofeffectively produced by auxiliary duct extension in conjunctiontherewith, thereby to increase noise reduction and maintain eifectivenozzle opening approximately constant.

8. The nozzle means defined in claim 7, wherein the trough-like elementsare open-ended fore and aft with the forward end thereof being openwithin the nozzle duct, and wherein the retracted auxiliary ductapertured discharge sides lie in proximate relation to the respectivetrough bases, and such elements have a deflecting side which thenextends forwardly and outwardly to the nozzle duct wall as a fairingsurface covering said open forward end, said retracted trough-likeelements respec- 7 tively being hinged at their forward ends at theirsides opposite said discharge sides, whereby said deflecting sidesbecome a scoop for directing gases into the auxiliry ducts whenextended.

9. The nozzle means defined in claim 7, wherein the trough-like elementsincrease progressively in depth to the exit plane of the nozzle and havean aperture in the base thereof located forwardly of said exit plane,hinged cover means normally covering said aperture and pivoted at theirrear edges on the nozzle duct, the retracted auxiliary ducts beingpivoted at their rearward inner corners in the trough-like elements at alocation therein situated just forwardly of said apertures and beingopen at least at their aft ends, whereby extension of said auxiliaryducts places them in communication with said aperture, and means toswing said cover means inwardly into transversely disposed position withextension of said auxiliary ducts, thereby to obstruct rearward gas flowbehind said aperture and direct such gases outwardly through saidaperture.

10. The nozzle means defined in claim 9, wherein the apertured dischargeside of the extended auxiliary ducts has louvers therein which slantrearwardly and outwardly, thereby to direct the gas discharge rearwardlyand outwardly, while permitting free inflow of slipstream air into andthrough the trough spaces with such auxiliary ducts retracted.

References Cited in the file of this patent UNITED STATES PATENTS2,845,775 Tyler et al Aug. 5, 1958 2,915,136 Ringleb Dec. 1, 19592,938,335 Cook May 31, 1960 2,940,252 Reihhart June 14, 1960 2,943,443Voyrnas et a1 July 5, 1960 FOREIGN PATENTS 211,954 Australia Dec. 13,1957

